Organic waste matter such as sludge, garbage and residues is one of today's major problems. It causes marine pollution, groundwater pollution, and eutrophication in rivers and lakes, as well as contamination of air and soil by environmental hormones such as dioxin, etc.
Significantly large plant and equipment investment is required to incinerate, melt or bury the sludge of sewage water which contains a large amount of hazardous heavy metals such as mercury and cadmium.
Currently used sludge treatment systems include, for example, the dehydration-drying-incineration system, the dehydration-drying-melting system or the dehydration-fermentation system. However, all of these systems leave residues such as incinerated ash, melted residues and/or residues containing hazardous heavy metals. Accordingly, a method for treating these final products has been required.
In order to solve this problem, the present inventor developed a method for fermenting organic waste by fermenting the organic waste and adding vegetal sludge thereto. See Japanese Patent Publication (Kokoku) No. 8-744.
Yet, there has been a demand for a method for treating organic waste matter which renders post-treatment unnecessary by reducing the amount of treatment residues.